As I note in my book (p.145 and p.118-119), the two obverses used for this
type should both be considered short busts and not heads.
Both varieties have a small round ring shown at the bottom front - this represents a
fibula and thus implies the representation of a shoulder. One variety - found at
Heracles,
Nicomedia and Cynics actually includes a small portion of the right shoulder, the other does not, but both have the
fibula.
SC